Rate limiting barriers for implantable devices and methods for fabrication thereof

Abstract

A coating for a medical device, particularly for a drug eluting stent, is described. The coating comprises a layer of an organic polymer component containing a therapeutic substance and a layer of an inorganic component for controlling the rate of release of the substance. The inorganic component according to embodiments of the invention includes gold or diamond-like carbon.

What is claimed is:  
     
         1 . A coating for a medical device, said coating comprising: 
 (a) a layer of an organic polymer component containing a therapeutic substance; and    (b) a layer of an inorganic component for reducing the rate of release of said therapeutic substance.    
     
     
         2 . The coating of  claim 1 , wherein said medical device is a stent.  
     
     
         3 . The coating of  claim 1 , wherein said organic polymer component is fabricated of a copolymer of ethylene and vinyl alcohol.  
     
     
         4 . The coating of  claim 1 , wherein said therapeutic substance comprises actinomycin D, estradiol, paclitaxel, docetaxel, or rapamycin.  
     
     
         5 . The coating of  claim 1 , wherein said layer of the inorganic component comprises gold.  
     
     
         6 . The coating of  claim 5 , wherein said layer of the inorganic component is modified with a passivating agent.  
     
     
         7 . The coating of  claim 6 , wherein said passivating agent is selected from a group consisting of an adduct of poly(ethylene glycol) with a thiol, a derivative of a hyaluronic acid, heparin, a derivative of heparin containing hydrophobic counter-ions, and a combination thereof.  
     
     
         8 . The coating of  claim 5 , wherein said layer of the inorganic component contains pores.  
     
     
         9 . The coating of  claim 1 , wherein said layer of the inorganic component is formed on said layer of the organic polymer component.  
     
     
         10 . The coating of  claim 1 , further including a polymeric coating disposed on said layer of the organic polymer component, wherein said layer of the inorganic component is formed on the polymeric coating.  
     
     
         11 . The coating of  claim 1 , wherein said layer of the inorganic component is fabricated of diamond-like carbon.  
     
     
         12 . A method for fabricating a coating for a medical device, the method comprising forming a coating on said device, said coating comprising a layer of an organic polymer component containing a therapeutic substance and a layer of an inorganic component for reducing the rate of release of said substance.  
     
     
         13 . The method of  claim 12 , wherein said medical device is a stent.  
     
     
         14 . The method of  claim 12 , wherein said layer of the organic polymer component is fabricated of a copolymer of ethylene and vinyl alcohol.  
     
     
         15 . The method of  claim 12 , wherein said therapeutic substance comprises actinomycin D, estradiol, paclitaxel, docetaxel, or rapamycin.  
     
     
         16 . The method of  claim 12 , wherein said layer of inorganic component includes gold.  
     
     
         17 . The method of  claim 16 , wherein said layer of inorganic component is deposited by sputtering, plasma deposition or spraying a suspension of gold in a polymeric material.  
     
     
         18 . The method of  claim 12 , wherein said layer of the inorganic component contains pores.  
     
     
         19 . The method of  claim 12 , further comprising modifying said layer of inorganic component with a passivating agent.  
     
     
         20 . The method of  claim 19 , wherein said passivating agent is selected from a group consisting of an adduct of poly(ethylene glycol) with a thiol, a derivative of a hyaluronic acid, a derivative of heparin, and a combination thereof.  
     
     
         21 . The method of  claim 11 , wherein said layer of the inorganic component includes diamond-like carbon.  
     
     
         22 . The method of  claim 21 , wherein said diamond-like carbon is deposited by chemical vapor deposition, ion beam assisted deposition, or molecular beam epithaxy.